Mercury-treated charcoal catalyst and process for its preparation



Patented Dec. 7, 1948 MERCURY-TREATED CHABCOA-L CATALYST AND PROCESS F-OR'ITS PKEPARAIION Leroy Frank Salisbury, Wilm-ington, l)c1., assignor to E. I. du Pont de Nemours & flomlpanygwilfmington, Del., a' corporation oI Dclawarc No DraWing-- cecal ap licatio ficrtembc 1945, .Serial-Np... 615,,090. Divided and this application July18f1947, Srial'No. 7625009 .s filaimsr (c1. ass-c211) This invention relates 13 a novel catalyst and to a process for obtaining the same. r

-Many catalysts consisting of catalytically active ,metals or their oxides, either alone or sup ported on suitable substrates, are known to ca-ta Me the reaction "between acetylene and-hydrogen fiuorideto produce vinyl fluorides. Particularly well known compositions are those obtained by impregnating charcoal with a suspension of mercuric oxide or by formation of the oxide in situ on the charcoal. 'In'the copending application of Leroy Frank Salisbury, Serial No. 508,243, filed October 29, "1943 (now U. S. Patent No.'2,426,792) highly useful charcoal supported mercury compound catalysts are disclosed as employable in the synthesis of vinyl fluoride and 2'-fluo'ro-'1 ;3- butadiene. Although these catalysts, and especially those disclosed in the -aiorementioned -ap' 'plication-of Leroy Frank Salisbury, are ad-vane tageously useful for their designed purpose, at

times they are characterized by certain disadvantages. "'T-hus,-a "large part of thetotal mercury present in the charcoal may be lost as free mercury during the catalyst preparation or opera,-

tion, thereby reducing-the activity of the catalyst;

Known charcoal-supported mercury catalysts,

such as may beprepa-red by roasting charcoal im-i pregnated with mercuric nitrate as disclosed in the aforementioned application of Leroy Frank Salisbury, although initially very active in the synthesis of 2-fiuoro-il;3butadiene, gradually become inactive. For instance, in 12 to16 hours these compositions may frequently lose as much as 50% of their initial activity.

This invention has as an object a charcoalsupported mercury catalyst wh' ich is not subject to the aforementioned disadvantages. A furt-her object is to provide a new and improved charcoalsupported mercury catalyst for preparing 2,-

fiuoro-1,3butad-iene -f-rom monovinylacetylene' and hydrogen fluoride, Additional objects will become apparent from an examinationof "the fol-- lowing'description-and claims.

These andQother objects and advantages are-ac-' complished according to the herein-described in i vention which comprises mercuric oxide-impreg nated o'harcoal coated with "basic mercuric nitrate.

Broadly,'the catalyst compositions of this in vention are obtained by impregnatingcharcoal with :mercuric oxide, drying, coating the mer curic oxide-impregnatedcharcoal withba'sic mercurie nitrate, and then drying the resulting composition.

In one preferred embodiment charcoal is im-' R 5 te. '-with an qu s u on cancers Thereafter said sall't is precipitated in situ as mercuric oxide, the resultant impregnated charcoal is=washed with water, dried at a temperature below C., contacted with an'aqueous suspension of 'basic mercuric nitrate, the concentration of said suspension being such as to provide a basic mercuric nitrate coating on said .charcoal in :an amount within :the range .of from two to 198 grams, calculated as elementary mercury, per liter vof charcoal and a total weight .of mercuric oxide and basic mercuric nitrate associated 'Wlth'said icha-rcoal within the range of from fourto 200 grams, icalculated as elementary mercury, :per liter of charcoal, and the resultant product is dried at :a temperature below 75 C.

The itollowing -examples, in which proportions are in parts by weight unless otherwise specified, are given for illustrative purposes and are-not in tended to place any restrictions on the hereindescribed invention.

Example I Charcoal sized to pass an 8-inch sieve but retained on a hi-mesh sieve was impregnated with agueousmercuric nitrate solutionusing g. of

mercuric nitrate, 4215 cc. of concentrated nitric acid, and 400 cc. of water per liter of charcoal. The productwas dried at room temperature until free of surface water and then stirred thoroughly with aqueous sodium hydroxide solution using 100 g. sodium hydroxide and one liter of water per liter of charcoal. The resulting product-was washed in distilled water for -24 hours, drained and aired-tied. Analysis showed the produotto contain 17.3% mercuric oxide.

The mercuric oxide-impregnated charcoal prepared as described above was stirred with a suspension of g. of basic mercuric nitrate in 325cc. of water for each two liters of charcoal. The product was then dried in vacuo at room temperature. Analysis showed it to contain 2.6% water, 26;-9% mercury,-and 052% nitrogen.

"The"basic mercuric nitrate employed above was prepared by adding with rapid stirrin aqueous sodium hydroxide solution to a solution of mercuric nitrate in aqueous nitric acid until the pH oi-the mixture was within-the range of from 3 to 3.5, ifoliowing which the precipitated basic mercuric nitrate was -filtered. off, washed with disti lednatepanddr edet "12 Example II A reactor consisting of a 1.5" x 21" iron pipe fitted at the top with a 1.5" pipe T with one opening of the T connected tea-sourceof monovinylacetylene and the other. to a source of hydrogen fluoride, was charge with 500 cc. of the catalyst prepared in Example 1. During '76 hours i a substantially uniform, dry mixtu re of 91g. of I 2-fluoro-l,3-butadiene, 1477 g." of, 'n'ionovinylacetylene, and about 565 g. hydrogen fluoride (a mol ratio of monovinylacetylene, to-hydrogen fluoride of 1 to 1.05), together'with two volumes of nitrogen per volume of the monov'inylacety-" lane/hydrogen fluoride mixture, was passed through the catalyst bed at a temperature within the range of 30-'75 C, at atmosphericpressure;

The contact time was about 45 seconds. Six

hundred twenty grams of monovinylacte1yene,930

g. of 2-fluoro-1,3-butadine, and 29 g. of 3,3-difiuoro-l-butene were obtained as products, corresponding to a 11% conversion to 2-fluoro-1,3- butadiene of the monovinylacetylene' passed, and a yield of 71% based on'the monovinylacetylene consumed. i

Example III I In contrast to the above, the most efficient HF, together with two volumes of nitrogen per volume of the monovinylacetylene/hydrogen fluoride mixture, was passed through the catalyst bed at a temperature within the range of 30 C. to 75 C. at atmospheric pressure and a contact time of about 45 seconds, The average conversion to 2-fluoro-1,3-butadiene obtained was 14% of the monovinylacetylene passed and the average yield-was 58%, based on the monovinylacetylene consumed.

Example V I i For still further comparison, a catalyst was madeby coating one liter of charcoal with a mixture of 100 g. of finely divided basic mercuric nitrate (made as described in Example I) in 400 cc. of water, followed by drying in vacuo at room temperature. Analysis of the product showed it to contain 2.5% water, 19.6% mercury, and 0.64%

nitrogen. I

Seven hundred and fifty cc. of the catalyst was charged into a 1.5" diameter iron pipe. During 65 hours, a substantially uniform, dry mixture of monovinylacetylene (containing 8% of Z-fluorocharcoal-supported mercury catalystjfor .the 12- of mercury pressure, and finally for .20 hours at 95 C. to 100 C, at one to. three mm. of mercury pressure. Duringrthis period oxides of.i nitrogen were evolved. Analysis showed that substantially all of the mercuryinitially present was re tained in the driedcatalyst and that the atomic ratio of mercury to nitrogen was about 120.55.

Seven hundred and fifty cc. of the above catalyst were charged into a 1.5"diameter iron pipe. During '70 hours, a substantially uniform dry mixture of monovinylacetylene (containing 6% 2- fluoro-1,3-butadiene) and hydrogen fluoride ,in

the mol .ratio of l CH2ICH-LCVECH to 1.25

together with two volumes of nitrogen per volume of monovinylacetylene/hydrogen fluoride mixture, was passed through the catalyst bed. at a temperature within the range of from- C. to 75 C, at atmospheric pressure and at a contact time of about seconds. fluoro-1,3-butadiene during this period of reaction was 18% of the monovinylacetylene passedat a yield of 65% based on the monovinylacetylene consumed.

, Example IV For further contrast with the catalysts of this invention, a catalyst wasprepared by adding charcoal impregnated with mercuric nitrate to excess aqueous sodium hydroxide, washing thoroughly with water, anddryin at room tempera ture in vacuo. Analysis showed-the product to I contain 2.5% water and 16.9 mercuric oxide.

Seven hundred and fifty cc. of the above-catalyst was charged into a 1.5" diameter ironpipe. During 78 hours, a substantially-uniform, dry mixture of monovinylacetylene (containing 5% of 2-fiuoro-l,3-butadiene) and hydrogenfluoride in the mol ratio of 1 CH2=CH+CHCH to 1.06

The conversion to 2-.

1,3-butadiene), and hydrogen fluoride in the mol ratio of 1 CH2=CHCECH to 1 HF, together with two volumes of nitrogen for each volume of I the monovinylacetylene/hydrogen fluoride mixture, was passed through the catalyst bed at a temperature within the range of 30 C. to 75 C, at atmospheric pressure and at a contact time of about 45 seconds. The average conversion. to 2-fluoro-1,3-butadiene based on the monovinyl-' acetylene passed was 16% and the yield was 51%, based on the monovinylacetylene consumed.

The mercuric oxide oxide impregnated, basic mercuric nitrate coated charcoal catalysts of this invention are particularly useful in the synthesis of 2-fluoro-1,3-butadiene from monovinylacetylene and hydrogen fluoride. may be made by any methodwhich does not lead to the formation of free mercury. In the preparation of such a catalyst, the charcoal may-be impregnated, with any water-soluble mercuric ,liter of charcoal.

salt, such as mercuric acetate, or a solution of mercuric chloride in aqueous hydrochloric acid, the impregnated charcoal then treated with an inorganic basic water soluble substance, e. g., an alkali metal carbonate, bicarbonate, hydroxide, oxide, etc., in amount suflicient to precipitate all of the mercury as the oxide, and the mercuric oxide impregnated charcoal is washed thoroughly to remove soluble salts, after which it is dried at a temperature below C., preferably at a temperaturebelow 75 C. The mercuric oxide impregnated charcoal thus obtained is coated with a suspension of basic mercuric nitrate, and the resulting product is dried at a temperature below 100 0., preferably at a temperature below 75 C. The concentration of mercuric oxide is within the range of from two to 198 grams, calculatedas elementary mercury, per liter of charcoal and of basic mercuric nitrate is within the range of from two to 198 grams, calculated as elementary mercury, per liter of charcoal, the total.concen-' tration of mercuric oxide and basic mercuric nitrate being within the range of from four to 200 grams, calculated as elementary mercury, per The preferred compositions from the standpoint of activityand'economical operation are those in which the total concen-- tration of mercuric oxide and basic mercuric ni-.

trate is within the range of from 50 to 100 grams,

calculated as elementary mercury, per liter of charcoal, the concentrations of mercuric oxide These catalysts awgsai andtfibasiemercuri nitrate e'achbeing within tri rangeot from" 2510' 75 grams, calculated as elementary m rcury; per liter ofthaircoal.

afrule, it is preferred to effect the drying of the catalystat ordinary pressures or under reduced pressures. Ifdes'ir'e'd, however, dryingcan' arations will fail because of the formation of free mercury. By drying below '75 C. almost no failures Will occur, and below about 50 C. failures due to mercury formation will be entirely eliminated.

As a support, charcoal derived from the incomplete combustion of animal or vegetable matter, e. g., wood, bone, nutshells, coconut, etc., is preferred for use. The active charcoal may be in granular or finely divided condition.

Although mercuric nitrate comprises the preferred type of mercury salt used in the impre nation of the charcoal, other water-soluble mercuric salts, as well as mixtures thereof, can be used. Thus, such salts as mercuric acetate, mercuric chloride, etc., can be used.

As a. rule, the amount of catalyst used in such that the reactor space is completely filled.

The hydrogen fluoride and acetylene should be passed through the catalyst bed at a space velocity such as to provide a contact time of to 100 seconds and preferably from 30 to 60 sec-.

ends.

The mol ratio of monovinylacetylene to hydrogen fluoride is generally within the range of from 1:2 to 2:1 and preferably is within the range of from 1:1.2 to 1:1. I

As previously indicated, the catalysts of this invention comprise mercuric oxide impregnated charcoal subsequently coated with preformed basic mercuric nitrate.

The catalysts of this invention are especially useful and efiicient for the synthesis of 2-fluoro- 1,3-butadiene from monovinylacetylene and hydrogen fluoride.

The process is generally operated at atmospheri-c pressure but if desired superatmospheric or subatmospheric pressures may be employed.

As many apparently widely difierent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims.

This application is a division of my application Serial No. 615,090 filed September '7, 1945 (now U. S. Patent No. 2,437,308)

Having described the present invention, the following is claimed as new and useful:

1. The process for obtaining a catalyst, which comprises impregnating charcoal with an aqueous solution of a mercuric salt, the concentration of said solution being such as to provide an impregnated charcoal containing said mercuric salt in an amount within the range of from two to 198 grams, calculated as elementary mercury, per liter of charcoal, then converting said salt in situ to mercuric oxide, drying the impregnated charcoal at a temperature below 100 C., thereafter contacting the charcoal with a suspension of basic mercuric nitrate, the concentration of said suspension being such as to provide a basic mercuric'nitr'a'te coating on said charcoal in an amount within the range of from two to 198 grams, calculated as elementary mercury, per liter of charcoal, and a total weight of mercuric oxide and basic mercuric nitrate associated with the charcoal within the range of from four to 200 grams, calculated as elementary mercury, perliter of charcoal, and drying the resultant product at a'temperature below'100" C.

2'. The process for obtaining a catalyst, which comprises impregnating charcoal with an aqueous solution of a mercuric salt, the concentration" of said solution being such as to provide an impregnated charcoal" containing said mercuric salt in anamount within the range of from two to 198 grams, calculated as elementary mercury, per liter of charcoal, thereafter precipitating said salt in situ as mercuric oxide, washing the resultant impregnated charcoal with water, drying said charcoal at a temperature below C., contacting the charcoal with a suspension of basic mercuric nitrate, the concentration of said suspension being such as to provide a basic mercuric nitrate coating on said charcoal in an amount within the range of from two to 198 grams, calculated as elementary mercury, per liter of charcoal, and a total weight of mercuric oxide and basic mercuric nitrate associated with the charcoal within the range of from four to 200 grams, calculated as elementary mercury, per liter of charcoal, and drying the resultant product at a temperature below 100 C.

3. The process for obtaining a catalyst, which comprises impregnating charcoal with an aqueous solution of a mercuric salt, the concentration of said solution being such as to provide an impregnated charcoal containing said mercuric salt in an amount within the range of from 25 to 75 grams, calculated as elementary mercury, per liter of charcoal, thereafter precipitating said salt in situ as mercuric oxide, washing the resultant impregnated charcoal with water, drying said charcoal at a temperature below 75 C., contacting the charcoal with a suspension of basic mercuric nitrate, the concentration of said suspension being such as to provide a basic mercuric nitrate coating on said charcoal in an amount within the range of from 25 to 75 grams, calculated as elementary mercury, per liter of charcoal, and a total mercuric oxide and basic mercuric nitrate concentration within the range of from 50 to 100 grams, calculated as elementary mercury, per liter of charcoal, and drying the resultant product at a temperature below 75 C.

4. The process for obtaining a catalyst, which comprises impregnating charcoal with an aqueous solution of mercuric nitrate, the concentration of said solution being such as to provide an impregnated charcoal containing said mercuric nitrate in an amount within the range of from 25 to 75 grams, calculated as elementary mercury, per liter of charcoal, thereafter contacting said impregnated charcoal with an aqueous sodium hydroxide solution whereby said mercuric nitrate is precipitated in situ as mercuric oxide, washing the resultant impregnated charcoal with water, drying said charcoal at a temperature below 50 C., contacting the charcoal with an aqueous suspension of basic mercuric nitrate, the concentration of said suspension being such as to provide a basic mercuric nitrate coating on said charcoal in an amount within the range of from 25 to 75 grams, calculated as elementary mercury, per liter of charcoal, and a total mercuric oxide and basic mercuric nitrate concentration within the 7 range of from 50 to 100 grams, calculated as elementary mercury, per liter of charcoal, and drying the resultant product at a temperature be-- 6. Charcoal impregnated with mercuric oxide in an amount within the range of from 25 110375 grams, calculated as elementary mercury, per liter of charcoal and coated with basic mercuric nitrate in an amount Within the range of from 25 to '75 grams, calculated as elementary mercury, per liter of charcoal, the total weight of mercuric oxide and basic mercuric nitrate associated with the charcoal being an amount within the range of from 50 to 100 grams, calculated as elementary mercury, per literof charcoal.

LEROY FRANK SALISBURY.

No references cited.

v Certificate of Correction Patent No. 2,455,881.

December 7, 1948. LEROY FRANK SALISBURY It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 28 Example I, for the word inch read mesh; column 3, line 6, ge read charged; column 5, line 30, Example V, for the words in such read is such,-

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the P atent Office. Signed and sealed this 14th day of June, A. D. 1949.

THOMAS F. MURPHY,

, Assistant Oomniasionar ofPatenta. 

